Chlorous acid groups

The quantitative stoichiometry of the D-glucose-chlorous acid reaction has been studied in detail the reagent used was sodium chlorite in a phosphoric acid-phosphate buffer at pH 2.4-3.4. The molar ratio of oxidant consumed to D-glucose consumed was 3 1 no overoxidation occurred over extended periods of time. The method is recommended for the determination of aldehyde groups in carbohydrates, especially alkali-sensitive carbohydrates. 

Carboxyl content was determined by the magnesium-ion-exchange method (5). For chlorous acid-treated pulp, the carboxyl group concentration was found to be 14.8 meq/100 g for sheets reduced with SBH, the carboxyl group concentration was 3.4 meq/100 g. Neither had any significant aldehyde group content the copper number (6) of the chlorous acid sheets measured 0.9 meq/100 g that of the SBH sheets measured 0.3 meq/100 g. 

An interesting observation was made by Davidson and Nevell when studying the cuprammonium fluidity of oxycelluloses partially oxidized with chlorous acid, namely, that the more-easily oxidized aldehyde group contributed more to the alkali lability. This is, in fact, further evidence for the existence of the hemiacetal with a six-membered ring (113) this has a i9-alkoxycarbonyl group and, from the work of Jayme and Maris, contains the more-easily oxidized aldehyde group. 

Oxidation of starch with chlorous acid produces an oxystarch (with carboxyl groups in uronic acid units, aldehyde groups formed from the primary hydroxyl groups, and ketone groups from the secondary hydroxyl groups) which is more sensitive to alkali than is chromic acid oxystarch. ... 

For isolation of hardwood xylans by way of holocellulose, a choice has to be made between the different methods available, according to the objectives to be attained. If molecular properties are to be investigated, the modified chlorine-2-aminoethanol method and, possibly, also the method of Klauditz are suitable. For chemical studies, especially if the location of the 0-acetyl groups is to be established, only chlorine dioxide or chlorous acid can be used. The subsequent extraction of the holocellulose will also have to be adapted to the desired ends. For isolation of a pure (4-0-methylglucurono)xylan, aqueous potassium hydroxide is excellent, since it gives almost quantitative yields and seldom causes removal of the gluco-mannan. If necessary, further purification can be effected by precipitation with Fehling solution. - ... 

Determination of carbonyl groups by reaction with hydroxylamine hydrochloride and titration of the liberated hydrochloric acid, or determination of aldehyde groups by oxidation with hypoiodite or chlorous acid and by reaction with diamines and subsequent fixation of dyes. 

Periodate-oxidized polysaccharides are sensitive to alkaline degradation but lose this property on reduction of the aldehydic groups to alcohols or on their oxidation to carboxylic acids with chlorous acid or bromine. 

Partial methylation of cyclohexa-amylose gave dodeca-O-methylcyclohexa-amylose in which all the primary and C-2 hydroxy-groups are etherified. O-Alkylated polymers obtained by treating cyclohexa-amylose with epichloro-hydrin under basic conditions catalysed the chlorination of anisole with hypo-chlorous acid, giving 4-chloroanisole with high (99%) regioselectivity. Dodeca-O-methylcyclohexa-amylose afforded greater selectivity than cyclohexa-amylose, and various features of the chlorination were discussed. 

Many common acids are oxoacids, i.e., molecules with the central atom surrounded by =0 (oxo) and -OH (hydroxo) groups. Perchloric (HC104), chloric (HC103), chlorous (HC102), and hypochlorous (HC10) acids... 

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